Calculating the load current and load voltage

  • Thread starter ainster31
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  • #1
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Homework Statement



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Homework Equations





The Attempt at a Solution



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For #2, how do I get VL and IL?
 

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  • #2
gneill
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For #2 you are to assume that ##V_L## is a given, along with ##V_{th}## and ##R_{th}##.
 
  • #3
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For #2 you are to assume that ##V_L## is a given, along with ##V_{th}## and ##R_{th}##.
By a given, you mean I just leave them as variables instead of giving them values, right?
 
  • #4
gneill
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By a given, you mean I just leave them as variables instead of giving them values, right?
Well, the Thevenin voltage and resistance should have numerical values that you calculated previously, but the ##V_L## is a new independent variable. You want to find an expression for ##I_L(V_L)##.
 
  • #5
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Would the below be correct?

I used mesh analysis.

$${ I }_{ L }=\frac { { V }_{ th }-{ V }_{ L } }{ { R }_{ th } }$$
 
  • #6
gneill
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Exactly like that :smile:
 
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  • #7
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For #4, I calculated IL, VL, and PL for RL=2200 ohms but I'm not sure how to get power transfer efficiency.

$$I_{ L }=1.745\cdot 10^{ -3 }A\\ V_{ L }=3.838V\\ P_{ L }=6.70\cdot 10^{ -3 }W$$
 
  • #8
gneill
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For #4, I calculated IL, VL, and PL for RL=2200 ohms but I'm not sure how to get power transfer efficiency.

$$I_{ L }=1.745\cdot 10^{ -3 }A\\ V_{ L }=3.838V\\ P_{ L }=6.70\cdot 10^{ -3 }W$$
Your power value looks a bit off, probably rounding/truncation error sneaking into your significant figures. Try keeping a few more decimal places in intermediate steps.

I'm not sure how they want you to define power transfer efficiency for this problem. Does your text give any examples?

Usually this sort of exercise would be leading up to a discussion of the Maximum Power Transfer Theorem. See if your text describes it; it may show you their definition of power transfer efficiency.
 

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